Cosmic distance inference from purely geometric BAO methods: Linear point standard ruler and correlation function model fitting
Abstract
Leveraging the baryon acoustic oscillations (BAO) feature present in clustering 2point statistics, we aim to measure cosmological distances independently of the underlying background cosmological model. However this inference is complicated by latetime nonlinearities that introduce model and tracer dependencies in the clustering correlation function and power spectrum, which must be properly accounted for. With this in mind, we introduce the "purely geometricBAO," which provides a rigorous tool to measure cosmological distances without assuming a specific background cosmology. We focus on the 2point clustering correlation function monopole, and show how to implement such an inference scheme employing two different methodologies: the linear point standard ruler (LP) and correlationfunction modelfitting (CFMF). For the first time we demonstrate how, by means of the CFMF, we can measure very precisely the soundhorizon/isotropicvolumedistance ratio, r_{d}/D_{V}(z ̄ ) , while correctly propagating all the uncertainties. Using synthetic data, we compare the outcomes of the two methodologies, and find that the LP provides up to 50% more precise measurements than the CFMF. Finally, we test a procedure widely employed in BAO analyses: fitting the 2point function while fixing the cosmological and the nonlineardamping parameters at fiducial values. We find that this underestimates the distance errors by nearly a factor of 2. We thus recommend that this practice be reconsidered, whether for parameter determination or model selection.
 Publication:

Physical Review D
 Pub Date:
 June 2019
 DOI:
 10.1103/PhysRevD.99.123515
 arXiv:
 arXiv:1811.12312
 Bibcode:
 2019PhRvD..99l3515A
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 12 pages, 2 tables